Diacetylenes can be coloured, or made to change colour, and have properties that make them suitable for use in sensors. Their use in multi-colour printing is disclosed in, for example, WO2006/018640. A particularly preferred diacetylene for this purpose is 10,12-pentacosadiynoic acid (PDA).
WO03/046050 discloses amide polymers with 10,12-PDA type side chains.